The proposed project is designed to continue a systematic investigation of the hypothalamic mechanisms of body weight regulation and feeding. The present investigator has reported that lesions of the lateral hypothalamus chronically lower the level at which an animal regulates its body weight, and furthermore, that the feeding interruption produced by such lesions is a behavioral strategy for reducing body weight to this lower level. Since the hyperphagia associated with lesions of the ventromedial hypothalamus is also secondary to a weight regulation adjustment--an elevated weight level-- our results led us to propose a body weight set-point analysis of the two hypothalamic feeding syndromes. Additional work has supported this weight set-point hypothesis and suggested a variety of additional analyses. The proposed program would simultaneously extend our research in several directions with a view to the development of a comprehensive explanation of the role of the hypothalamus in weight regulation and feeding. The experiments would provide: (a) a more complete examination of the nature of the hypothalamic weight regulation mechanism(s), (b) an examination of the subtle regulatory disturbances reported to accompany damage to the hypothalamus, (c) a critical examination of hypothalamic "finickiness", (d) examination of an explanation of the lesion-produced weight alterations in terms of the hypothalamic control of adipose tissue metabolism, and (e) application of a new anatomical mapping procedure developed by the principal investigator to the hypothalamic feeding and weight regulating areas. The weight set-point hypothesis has proved the most parsimonious explanation of the hypothalamic feeding syndromes. The hypothalamic regulation of body weight and adiposity promises to be of fundamental interest in its own right. The research we propose represents a program addressed to a thorough examination of both of these questions.